The conversion of the diterpenoid resin acid, podocarpic acid, into a tetracyclic system possessing a 5-membered ring D is described. The unsubstituted ring with a CO group at C-151 was prepared from the 13-(2′-carboxyethyl) derivative III (R  CH2CH2CO2H) in fair yield, but attempted cyclization of compounds possessing a 1′-substituted-2′-carboxyethyl side chain at C-13 was unsuccessful. The C-17
                                    描述了将二萜
树脂酸,罗汉果酸转化为具有5元环D的四环体系。由13-(2'-羧乙基)衍
生物III(RCH 2 CH 2 CO 2 H)以合理的产率制备了在C-15 1处带有CO基团的未取代环,但尝试将具有1'的化合物环化C-13的-取代的2'-羧乙基侧链不成功。从13-
丙烯酰基化合物以低收率获得C-17酮,但从13-
巴豆酰基化合物根本得不到。描述了一些涉及
苯甲醚衍
生物的模型实验。